Brain, spleen, and selected lymph nodes from sheep with clinical signs of scrapie were analyzed for presence of proteinase K-resistant protein (PrP-res). Diagnosis of scrapie on the basis of detection of PrP-res was compared with diagnosis on the basis of histologic evaluation of the brain from clinically affected or exposed sheep. Proteinase K-resistant protein was found in every brain that was histologically positive for scrapie, and in addition, was found in the brain of several clinically positive sheep that were not diagnosed as scrapie-positive by histologic evaluation. Proteinase K-resistant protein was also found in 87% of the spleens and lymph nodes from sheep that had PrP-res detected in brain homogenates. Therefore, analysis of sheep brain, spleen, or lymph nodes for PrP-res provided a diagnostic approach that was superior to histologic examination alone for detection of naturally scrapie agent-infected sheep.

The alpha 1-proteinase inhibitors of trypsin, Spi1, Spi3A, and Spi3B, in bronchoalveolar lavage fluid (BALF) and serum of horses were separated by electrophoresis, and their proportions were quantified in 12 control horses and 12 with chronic obstructive pulmonary disease (COPD). A significantly lower proportion of Spi3B (P < 0.05) and higher proportion of Spi1 (P < 0.02 to P < 0.01) were detected in BALF, compared with serum, in control and COPD-affected horses and appeared to be attributable to reduced Spi3 activity in BALF. There was no significant difference between the control and COPD groups in this respect, indicating that the decrease in Spi3 may be a physiologic phenomenon. The differences observed may be associated with proteolytic damage to or preferential complex formation by Spi3.

The proteolytic activities present in midguts of both fed and unfed Haemaphysalis longicornis were assessed by using the gelatin-substrate gel electrophoresis and inhibitor sensitivity analyses. Three predominant (116, 48 and 40 kDa) and two weak (55 and 60 kDa) proteinase bands were commonly expressed in both unfed and fed ticks, while a weak 80 kDa band was only present in fed ticks. Consistent with observations on other tick species, proteolytic activity against the gelatin substrate was observed only under acidic conditions. Inhibition studies against the gelatin substrate using a panel of inhibitors showed that the predominant proteolytic enzymes of 40 and 48 kDa molecular mass are cysteine proteinases. These results are discussed in the context of host vaccination as an alternative tick control method to the current use of chemical acaricides